The subject matter of patent application U.S. Ser. No. 584,011 is contained herein by reference in its entirety and forms part of this disclosure. In that application there is described and claimed apparatus and methods for providing indicia and control signals as a function of slip of an induction motor under load. This provides monitoring over an analog range of load conditions on the motor where specified load conditions within said range can be selected for alarm and control functions by electronic techniques.
However, this prior application and other prior art techniques are generally limited to periodically recurring functions measured from rotating shafts and do not provide for analog load monitoring over a range of load conditions where the prime mover may work intermittently, or where instantaneous sampling may be desired such as when a linear movable element such as the shaft of a hydraulic piston is used to drive a load.
Speed monitoring control devices such as those of U.S. Pat. No. 3,184,606, May 18, 1965 or U.S. Pat. No. 3,739,367, June 12, 1973 do not provide an adequate capability either of operation over a selected range of speed conditions or for intermittently sampling speed at predetermined times, nor do they provide any means for a continual visual monitor of speed being encountered.
Furthermore, speed monitoring devices are primarily governors indicating a single speed condition which are not adapted to work over an analog range of load conditions. Such devices are not readily adaptable to choice of different load conditions at which controls may be effected or for display of variations of load conditions within a load range.